Using recombinant DNA technology, protein products can be produced in large quantities. One of the preferred methods of accomplishing this is to express the protein intracellularly. This may result in production of large quantities of insoluble, intracellular protein found in inclusion bodies, for example in the case of expression of fusion proteins. Although such proteins may not be native in structure, they can sometimes be renatured or used "as is," e.g. for immunodiagnostics. The major advantage of this approach is that it can yield very high levels of product.
Recombinant proteins produced as insoluble products in inclusion bodies have solubility properties that may interfere with their purification. These proteins generally require use of a denaturant, chaotrope or detergent for solubilization. In some cases, these treatments prevent the use of certain chromatographic procedures for purification, such as ion exchange. In addition, these treatments can solubilize non-proteinaceous contaminants that interfere with downstream processing, such as high molecular weight carbohydrates that may increase the viscosity of the solution.